Did the prophet say this regarding fasting in the day of Ashura?

I have heard that when the prophet met the people of the book, he asked them why they were fasting in the day of Ashura. They replied that it was a good day. The prophet then said he would fast that day and he added that **he would observe two fasts in the next Ashura (in the next year) if he is alive.** Did he say that? Did he say that he would observe two fasts in the next Ashura? Is it a weak hadith that says this or something similar?